The cardiac muscle cells of the heart (called the myocardium) are tightly bound together in layers and encircle the blood filled chambers of the heart. When the heart contracts the myocardium encloses on the blood filled chambers and blood is propelled around the body. With greater filling of blood (i.e. increased end diastolic volume; EDV) the force of contraction of the heart is subsequently greater. Experiments in the late 19th century, using frog hearts, demonstrated this ability of the heart, known as the Frank-Starling Law of the heart, named after Otto Frank and Ernest Starling. The heart requires a number of important resources to carry out its role. Calcium, oxygen and adrenaline are all required for normal functioning and any changes in their levels can affect the force of contraction.
This simulation will prepare you for the first BMS2031 practical class, called ‘Contraction of Cardiac Muscle’ (in week 2 of semester). It is based on recordings taken during this practical class in previous years. This practical uses isolated strips of toad ventricular muscle that are electrically stimulated to contract. The force of cardiac muscle contraction is recorded (with grams of tension of the Y axis and time in seconds on the X axis of the recording). Experiments in this simulation will examine the effects of:
1. changing the cardiac muscle length
2. changing the extracellular calcium concentration
3. oxygen deprivation, and,
4. the drugs adrenaline and nifedipine on the force of cardiac muscle contraction.
View the video below before commencing these simulations.